Post-transfusion purpura: a challenging diagnosis.

BACKGROUND: Post-transfusion purpura is a rare syndrome characterized by severe thrombocytopenia and bleeding caused by alloimunization to human platelet specific antigens following a blood component transfusion. The suggested incidence is 1:50,000-100,000 transfusions, most often occurring in multiparous women. The diagnosis is not easy because these patients, who are often critically ill or post-surgery, have alternative explanations for thrombocytopenia such as infection, drugs, etc. OBJECTIVES: To describe patients with initially misdiagnosed PTP and to emphasize the diagnostic pitfalls of this disorder. PATIENTS AND RESULTS: During a period of 11 years we diagnosed six patients with PTP, four women and two men. The incidence of PTP was approximately 1:24,000 blood components transfused. We present the detailed clinical course of three of the six patients in whom the diagnosis was particularly challenging. The patients were initially misdiagnosed as having heparin-induced thrombocytopenia, systemic lupus erythematosus complicated by autoimmune thrombocytopenia, and disseminated intravascular coagulation. A history of recent blood transfusion raised the suspicion of PTP and the diagnosis was confirmed by appropriate laboratory workup. CONCLUSIONS: PTP seems to be more frequent than previously described. The diagnosis should be considered in the evaluation of life-threatening thrombocytopenia in both men and women with a recent history of blood transfusion.